What does it mean to eat kosher (hebr. : כ ש ר) ? The pure and holy table – Haschulchan ha tahor we hakadoschby Rabbi Yitshak Ehrenberg, Rabbi of the Jewish Community in Berlin und Member of the board of the Orthodox Rabbi Conference Germany :

Taking care of what people eat, sanctifies them. The Torah says that respecting and observing the Jewish dietary laws (kashrut) sacrifies the human being. Any impure food entering ones’ body contaminates his soul and influences ones‘ spiritual condition. Therefore the pure table has always been the fundament of a Jewish home. At the time „kashrut“ became the meaning of permitted food, kosher = correct, right. Further meanings were added: glatt kosher, kosher le mehadrin, le mehdrin min hamehadrin. There are various categories to the different degrees of the kashrut, everyone on his own way.

Eating kosher means, observing the kashrut :

Only meat from particular species is permissible:Mammals that both chew their cud (ruminate) and have cloven hooves can be kosher, e.g. cow, goat, sheep. Animals with one characteristic but not the other (the camel, the hyrax and the hare because they have no cloven hooves, and the pig because it does not ruminate) are specifically excluded. The animal has to be ritually slaughtered (shechted).